Method and composition for detecting oxidizing salts

ABSTRACT

The present invention provides methods for determining the presence of oxidizing salts. According to the current invention, analyte is collected on a swipe and subsequently heated to a temperature sufficient to release a detectible vapor phase component of the oxidizing salt. The vapor phase component passes reacts with a pH sensitive molecule. Reaction of the vapor phase product with the pH sensitive molecule produces a detectible change in response intensity.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/650,820 entitled METHOD AND COMPOSITION FOR DETECTING OXIDIZINGSALTS, filed Oct. 12, 2012.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

Oxidizing salts such as but not limited to ammonium nitrate, ammoniumperchlorate, and urea nitrate have many industrial uses. Unfortunately,these strong oxidizing compounds may also be incorporated into homemadeexplosive devices. In particular, a high explosive known as ANFO(ammonium nitrate fuel oil) is easily prepared by combining ammoniumnitrate with number two fuel oil or diesel fuel. A typical formulationfor ANFO utilizes about two quarts of fuel oil and about fifty pounds ofammonium nitrate. Although commonly used in the mining industry, thesimple process for preparing ANFO also makes it a ready formulation forterrorists. Thus, the ability to readily detect the presence ofoxidizing salts will be beneficial to the detection and prevention ofattacks using explosives based on oxidizing salts.

SUMMARY OF THE INVENTION

The current invention provides a method for detecting oxidizing salts.The method utilizes a pH sensitive molecule that undergoes a reversiblereaction with an acid component of a vaporized oxidizing salt. Themethod of the current invention includes the steps of collecting asample of an oxidizing salt. The collected sample is presented to asensor assembly. The sensor assembly includes a solid substrate carryingthe pH sensitive molecule; an excitation source, providing stimulatingradiation at wavelengths selected for the type of pH sensitive molecule,and a light sensor monitoring the response intensity of the pH sensitivemolecule to the stimulating radiation. Typically, the excitation sourcewill operate at wavelengths between about 325 nm and about 700 nm, inone embodiment the excitation source operates at wavelengths betweenabout 365 nm and about 410 nm. The collected oxidizing salt is heated toa temperature sufficient to evaporatively dissociate the oxidizing saltyielding evaporative dissociation compounds, i.e. the acid and basecomponents, of the oxidizing salt. Following evaporative dissociation, asufficient quantity of the acid component reacts with the pH sensitivemolecule producing a change in response intensity of the pH sensitivemolecule detectible by the light detector. Monitoring of the responselevel during the reaction of the pH sensitive molecule with the acidcomponent wherein a response change of about three times a controlledresponse or more indicates the presence of an oxidizing salt.

In another embodiment, the present invention provides a method fordetermining the presence of oxidizing salt on a surface. According tothis method, sampling material is brought into contact with a surfacesuspected of carrying an oxidizing salt selected from the groupconsisting of ammonium nitrate, urea nitrate, guanidine nitrate andammonium perchlorate thereby collecting a sample from said surface. Thesampling material is presented to a sensor assembly including a heatersuitable for inducing evaporative dissociation of the oxidizing saltinto its acid and base components. The sensor assembly includes a solidsubstrate carrying the pH sensitive molecule; an excitation source,providing stimulating radiation at wavelengths selected for the type ofpH sensitive molecule, and a light sensor monitoring the responseintensity of the pH sensitive molecule to the stimulating radiation.Typically, the excitation source will operate at wavelengths betweenabout 325 nm and about 700 nm, in one embodiment the excitation sourceoperates at wavelengths between about 365 nm and about 410 nm. Operationof the excitation source stimulates the pH sensitive molecule to producea detectible response. During presentation of the sampling material tothe sensor assembly, monitoring the response of the pH sensitivemolecule to the stimulation with a light sensor suitable for detectingchanges in response intensity. The step of heating releasing theevaporative dissociation components which pass into said sensorassembly. Once within the assembly at least one component reacts withthe pH sensitive molecule. During the step of reacting at least onedissociation component with the pH sensitive molecule, the light sensormonitors the pH sensitive molecule for a change in response intensitywhen compared the intensity of response in the absence of a dissociationcomponent thereby indicating the presence of an oxidizing salt on thesampled surface.

Still further, the present invention provides a detector assemblyconfigured to detect trace amounts of evaporative dissociation compoundsderived from an oxidizing salt. The detector assembly comprises a sensorassembly including a solid substrate carrying a pH sensitive molecule,an excitation source positioned to provide stimulating radiation to thepH sensitive molecule, a light sensor and a first heater suitable foradjusting the temperature of the sensor assembly. The excitation sourceis a pH sensitive molecule dependent capable of providing stimulatingradiation at wavelengths between about 325 nm to about 700 nm to the pHsensitive molecule. The light sensor is suitable for detecting responseintensity changes at wavelengths between about 360 nm and about 750 nmand positioned to monitor the response of the pH sensitive molecule tostimulation by the excitation source. The detector assembly alsoincludes a sampling tip assembly in fluid communication with the sensorassembly. A second heater is associated with the sampling tip assembly.The second heater is suitable for maintaining the temperature of thesampling tip assembly at a temperature between about 90° and 350°.Additionally, the detector assembly includes a gas movement pump influid communication with the sampling tip and the sensor assembly. Thegas movement pump configured to move vapors from the sampling tipassembly to and along the solid substrate of the sensor assembly.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 provides a schematic view of one configuration of the currentinvention.

FIG. 2 provides a schematic view of an alternative configuration of thecurrent invention.

FIG. 3 depicts pH sensitive molecule increase in response intensity.

FIG. 4 depicts maximum percent response for ANFO, nitric acid, ammoniumnitrate and urea nitrate.

DETAILED DISCLOSURE OF THE CURRENT INVENTION

Heating oxidizing salts, such as ammonium salts and urea salts, producesvapor phase basic and acidic components via a process known asevaporative dissociation (also known as thermal dissociation). Forexample, ammonium nitrate undergoes evaporative dissociation attemperatures below the melting point of 170° C. Evaporative dissociationof oxidizing salts produces the respective acid and basic components ofthe salt. Certain oxidizing salts are known to have significant vaporpressures at temperatures less than their melting points. For example,the vapor pressure of solid ammonium nitrate at 100° C. is 0.0024 mmHgand the vapor pressure increases to 1.17 mmHg at 165° C.

To demonstrate the ability to induce evaporative dissociation of anoxidizing salt, solid ammonium nitrate was subjected to evaporativedissociation at 170° C. Subsequently, downstream condensation of theresulting vapor components produced ammonium nitrate. For the six hourtest period, the condensed, reformed ammonium nitrate showed only a0.12% decomposition loss in the sample compared to the initialconcentration of ammonium nitrate. The same experiment at 240° C.resulted in 15% of the sample decomposing into NO₂, N₂O, and NO, andwell as H₂O and N₂. Therefore, heating the solid ammonium nitrate aboveapproximately 100° C. will induce evaporative dissociation of at least aportion of the solid ammonium nitrate to ammonia gas (NH₃) and nitricacid (HNO₃) while heating at temperatures greater than the compoundsmelting point decomposes the compound.

Thus, one can determine the presence of trace amounts of ammoniumnitrate by heating the ammonium nitrate above 100° C. and subsequentlydetecting the presence of the vapor phase components. The temperature ofevaporative dissociation for other oxidizing salts can be readilydetermined by standard industry methods. For example, ammonium nitrateis has a melting point of 170° and an extrapolated room temperaturevapor pressure of 4.3×10⁻⁷ torr. The temperature range suitable forinducing evaporative dissociation of ammonium nitrate is about 100° C.to about 170° C. Urea nitrate has a melting point of 133° C. and anextrapolated room temperature vapor pressure of 6.6×10⁻⁷ torr. Thetemperature range suitable for inducing evaporative dissociation of ureanitrate is about 80° C. to about 133° C. Guanidine nitrate has a meltingpoint of 213° C. and an extrapolated room temperature vapor pressure of4.6×10⁻¹⁴ torr. The temperature range suitable for inducing evaporativedissociation of guanidine nitrate is about 200° C. to about 225° C.Additionally, the evaporative dissociation temperature range forammonium perchlorate is about 250-350° C.

The method of the current invention involves initially sampling a targetarea suspected to be contaminated with an oxidizing salt using asampling material suitable for collecting oxidizing salts. Non-limitingexamples of sampling materials suitable for collecting oxidizing saltsfrom a target area include non-reactive polytetrafluoroethylene swipesand other substrates substantially non-reactive with the suspectedoxidizing salt and its components that have the ability to collect tracesamples of oxidizing salts and will not decompose at the indicatedoperating conditions. Due to their ability to conform to irregularsurfaces, polytetrafluoroethylene swipes are particularly suited for themethod of the present invention. Subsequent heating of the samplingmaterial, now carrying the oxidizing salts, will induce evaporativedissociation of the salt releasing the salt's acid and base componentsfrom the sampling material. Optionally, high volume collection of vaporand particles that can be heated may be carried out using a vortexsampler with a screen capture. Alternatively, the surface suspected ofcarrying oxidizing salts may be heated to release the dissociationcomponents for collection by the sampling assembly.

The method of the current invention utilizes a sensor which incorporatesa pH sensitive molecule. An example of a suitable pH sensitive moleculeis 2-[5-methoxy-2-(4-phenyl-quinoline-2y1)-phenyl]-ethanol asrepresented by the following structure:

However, other suitable compounds include, but are not limited to:

SNARF®-5F, 5-(and-6)-carboxylic acid as represented by the followingstructure where the carboxylic acid group may be positioned at eitherthe indicated 5 or 6 position,

SNARF®-4F, 5-(and-6)-carboxylic acid as represented by the followingstructure where the carboxylic acid group may be positioned at eitherthe indicated 5 or 6 position,

5-(and-6)-carboxy SNARF®-1, as represented by the following structurewhere the carboxylic acid group may be positioned at either theindicated 5 or 6 position,

LysoSensor™ Green DND-153 as represented by the following structure,

2′,7′-difluorofluorescein (CAS #195136-58-4) as represented by thefollowing structure,

and, 2-{2-[-(tert-butyl-dimethyl-silanyloxy)-ethyl]-4-methoxy-phenyl}-4-phenyl-quinoline as represented by the followingstructure

SNARF® is a registered trademark of Invitrogen, INC., 4849 PitchfordAvenue Eugene Oreg. 97402, for fluorescent dye used in scientificresearch to measure pH.

The above referenced compounds will fluoresce in response to anexcitation source such as a mode locked light source, i.e. a UV LED or ablue LED or a mode locked laser that emits light radiation atwavelengths between about 325 nm and about 700 nm See column 16, lines14-67 of U.S. Pat. No. 6,558,626. The entirety of U.S. Pat. No.6,558,626 is incorporated herein by reference. In the preferredembodiment, the pH sensitive molecule along with a polymer material,such as but not limited to polyethylene, polyisobutylene, celluloseacetate, polystyrene, polyvinyl chloride, polydimethylsiloxane, andphenyl containing siloxane copolymers are spin-coated on the interior ofa glass capillary. Thus, the method of the current invention is readilyadaptable for use within the detector assembly described by U.S. Pat.No. 6,558,626.

With reference to FIGS. 1 and 2 and as discussed at column 3, lines25-58 of the '626 patent, the detector assembly 10 comprises a housing12, a gas movement pump 14 and a sensor assembly 16. Pump 14 providesthe ability to move vapors from the tip or entrance 22 to the detectorassembly and by the solid substrate 24 within the sensor assembly 16.Additionally, detector assembly 10 includes a heated tip assembly 26which provides fluid communication between the exterior of the detectorassembly housing 12 and ultimately to sensor assembly 16. Tip assembly26 can be a bare heated inlet or even a sample desorber 27 that heats asample collection material 28 without requiring the user to press saidsample collection material 28 against the hot inlet tip 22.

Positioned within the sensor assembly is a short pass filter 41 locatedbetween the excitations source 32 and the solid substrate 24, a longpass filter 42 located between solid substrate 24 and the light detector34 or suitable sensor. As known to those skilled in the art, short pass41 and long pass 42 filters manage the wavelengths of radiation reachingsubstrate 24 and light sensor 34. Solid substrate 24, such as but notlimited to a glass capillary, a flat plate of plastic, glass or othernon-reactive support material carries the pH sensitive molecule 25 andoptionally carries a hydrophobic polymer or plasticizers selected from,but not limited to, polyethylene, polyisobutylene, cellulose acetate,polystyrene, polyvinyl chloride, polydimethylsiloxane, and phenylcontaining siloxane copolymers.

FIG. 1 schematically depicts a configuration utilizing a glass capillaryas solid substrates 24 and FIG. 2 schematically depicts a configurationusing a flat substrate as solid substrate 24. As depicted in FIG. 2, pHsensitive molecule 25 can be applied as a generic zone or as acontinuous strip across the substrate. Detector assembly housing 12 isconfigured to provide fluid communication between solid substrate 24 andheated tip assembly 26. Sensor assembly 16 also includes the excitationsource 32 and a light detector 34 or sensor suitable for detectingchanges in response intensity of the pH sensitive molecule atwavelengths between about 325 nm and about 700 nm. Thus, sensor assembly16 provides the ability to detect increases or decreases in responseintensity of the pH sensitive molecule during excitation by theexcitation source in response to the presence of an acid component of anoxidizing salt. Associated with sensor assembly 16 and light detector 34is a display 43 suitable for displaying the response of light detector34. Display 34 may be integral with detector assembly 10 or a separatecomponent therefrom. Additionally, one skilled in the art willappreciate that control of detector assembly 10 will be managed by aproperly programmed computer processor (not shown).

Sensor assembly 16 and tip assembly 26 each have associated heat sources36 and 38. During the practice of the current invention, heat source 38associated with tip assembly 26 maintains inlet tip 22 or sampledesorber 27 operational temperature at a temperature sufficient toinduce evaporative dissociation of the suspected analyte. For example,tip temperatures for ammonium nitrate will be between about 100° C. toabout 170° C. Typically, tip temperature will be above 120° C.Generally, the tip operational temperature is from about 130° to about170°. Note, sample desorber 27 may include its own heat source 38 athereby precluding the need to contact sample collection 28 directlyagainst heated tip 22. Heat source 36 associated with sensor assembly 16generally maintains the sensor assembly between about 25° C. to about100° C. More typically, sensor assembly 16 will operate at a temperaturebetween about 35° C. to about 85° C. with the most common operationaltemperature being about 45° C. to 70° C. At these temperatures, the flowrate of the vapors through sensor assembly 16 will precludecondensation. The preferred sensor assembly operating temperaturemaximizes performance of the pH sensitive molecule. The preferredoperating temperature range will maximize fluorescent response anddetection.

Optionally, the method of the current invention also includesestablishing an initial response baseline also known as a controlledresponse for the pH sensitive molecule. To establish the baselineresponse for the pH sensitive molecule the user activates the excitationsource and heaters allowing each to achieve operational conditions. Thenthe user presents the coated solid substrate 24, free of oxidizing salt,to detector assembly 16 producing a possible detectible response fromthe pH sensitive molecule. Thus, any response resulting from thisprocess is free of influence from an acid component.

For example, a controlled response suitable for establishing a baselinecan be produced from the pH sensitive molecule by presenting samplecollection material 28 (e.g. swipe, vortexed air collection, wire meshor wire screen) to the operating detector assembly. The responsegenerated by the pH sensitive molecule to sample collection material 28that is free of oxidizing salts is generally repeatable and predictable.Therefore, the result can be used to cancel out background noise in thesensor assembly. Background cancelation in the data analysis programmingresults in a cleaner real-time output display desired in product readydevices. The controlled response establishment step uses ambientconditions. Following the establishment of the controlled response,subsequent changes in response intensity from the pH sensitive moleculecan then be attributed to the presence of a vapor phase acid componentof an oxidizing salt in the gas passing through the detector assembly.

Following establishment of the baseline and heating the tip to theindicated range for the oxidizing salt suspected to be on the surface ofinterest. For example, when ammonium nitrated is suspected to be on thesurface, the sampling tip assembly will be heated to a temperaturebetween about 120° C. and about 170° C. When the tip assembly hasreached the desired temperature, sample collection material 28 carryingcollected trace amounts of an oxidizing salt 23 is presented to the tipassembly of the detector. Contact with the heated tip assembly inducesevaporative dissociation of the oxidizing salt into its basic and acidiccomponents. A pump pulls the vapor phase components into the detectorand passes the components over the pH sensitive molecule. Upon reactionof the acidic component with pH sensitive molecule, the pH sensitivemolecule situated upon a solid substrate will undergo a change inresponse intensity. The light sensor within the sensor assemblyregisters the change in response intensity of the pH sensitive moleculethereby establishing the presence of an oxidizing salt on the samplingmaterial. In general, collecting and presenting about five to about 50nanograms of oxidizing salt to the tip will generate a sufficientquantity of the acid component to produce a positive result.

Thus, exposure of oxidizing salts on the sampling material to the tipassembly operating at the indicated temperatures will induce evaporativedissociation releasing the detectible acid component of the salt.Oxidizing salts detectible by the disclosed process include ureanitrate, ammonium nitrate, ammonium perchlorate and guanidine nitrate.Additionally, the method of the present invention will detect theammonium nitrate portion of ammonium nitrate/fuel oil mixtures.

During operation and detection, a pump within the detector pulls air inthrough the heated tip assembly passing it to the solid substratecarrying the pH sensitive molecule within the sensor assembly.Typically, this pump operates at a flow rate between about 10 cm³/minuteand about 200 cm³/minute. More commonly, the flow rate through thesensor assembly will be between about 20 cm³/minute and 60 cm³/minute.In general, the flow rate is selected to ensure sufficient residencetime of the acid component in the glass capillary and to precludecondensation of the vapor components within the detector assembly.Operation of the detector in the described manner will permit sensing ofoxidizing salts on the sampling material as low as about 5 nanograms.Typically, response time from exposure of the oxidizing salt to the tipto a positive response ranges from less than one second up to about tenseconds.

EXAMPLE 1 Detection of Ammonium Nitrate

A response baseline for the pH sensitive molecule was established bysampling ambient air. A ten nanogram sample of ammonium nitrate wasapplied to a polytetrafluoroethylene swipe by pipetting a small volumeof a methanol solution. The swipe was placed in the flow path directlyin front of the solid substrate, in this case a glass capillary and thenheated to 145° C. by contact with the hot inlet tip of the sensor. Theglass capillary was spin-coated with2-[5-methoxy-2-(4-phenyl-quinoline-2yl)-phenyl]-ethanol combined withphenyl containing siloxane copolymers. A pump operating at 30 cm³/minutewas actuated and the evaporative dissociation products, in vapor form,were carried through the spin-coated capillary. The excitation sourcewas a 405 nm source and the light sensor was a 435 nm long pass. Asreflected in FIG. 3, under these conditions the pH sensitive moleculeexperienced a marked increase in response intensity over the establishedbaseline.

The above testing method was repeated using polytetrafluoroethyleneswipes carrying ammonium nitrate/fuel oil (ANFO) and swipes carryingurea nitrate. In each instance, the pH sensitive molecule underwent adetectable increase in response intensity. Using the above procedure,ANFO was detectible at a concentration of about 8 ng and urea nitrate ata concentration of about 5 ng. See Table 1. Based on the resultingincrease in response, approximately 30% of the oxidizing salt in eachsample underwent evaporative dissociation.

EXAMPLE 2

A field test was performed where small amounts of dry ammonium nitrate(AN), urea nitrate (UN), and ANFO were fingerprint transferred (touch byhand and then transferred) to the surface of glass, plastics, cardboardand metals. A polytetrafluoroethylene swipe was dragged across eachcontaminated surface to transfer the powder to the swipe. The swipe wasthen presented to or inserted into a tip assembly in connection with adetector equipped with a pH sensitive molecule modified sensing element.The results shown in FIG. 4 and Table 1 depict the percent change inresponse intensity and compares to the same amount to nitric acid. Eachtest sample produced a positive response as reflected by the increasedresponse intensity.

TABLE 1 Limits of detection (with 10% response intensity increaserepresenting the lowest detectable response) Extrapolated Mass Limit ofAnalyte Tested Detection Notes Nitric acid 1 ng 1 ng Measured 10%response intensity increase for 1 ng Ammonium 33 ng 7.7 ng Measured 43%average nitrate response intensity increase for ten 33 ng samplesAmmonium 1 ng, 7.7 ng Measured 0.8% response nitrate fuel 10 ngintensity increase from 1 ng oil and 35% from 10 ng samples Urea 1 ng,4.8 ng Average 2.9% response nitrate 100 ng intensity increase from 1 ngand 164% from 100 ng samples

EXAMPLE 3

The following example confirms the evaporative dissociation of nitricacid from ammonium nitrate. GC/MS techniques were used to identify themass spectrum for nitric acid. Concentrated nitric acid was passedthrough a prepless sample introduction probe (PSI probe) and guardcolumn setup on a 1200 L triple quadrupole instrument. The PSI-Probeallows solid materials to be introduced in the GC instead of injectingsolutions. The spectrum for pure nitric acid revealed a base peak of 46m/z with a small molecular ion peak at 63 m/z, approximately 1% of theheight of the base peak where m/z is mass-to-charge ratio. In order toincrease the molecular ion abundance and therefore increase theconfidence in discriminating nitric acid from other analytes, thermalanalysis was conducted on an ion trap GC/MS system utilizing methanechemical ionization. With this setup, the ratio of the nitric acid'sprotonated molecular ion, 64 m/z, to the 46m/z base peak, wasapproximately 13%.

A small amount of ammonium nitrate was placed into the injector of theion trap GC/MS instrument via a PSI probe. When the injector was heatedto 150° C., NO₂ and nitric acid were both detected. The ratio ofprotonated molecular ion (64 m/z) to 46 m/z was much lower than the 13%observed for neat nitric acid, due to evolution of NO₂ in addition tonitric acid produced from ammonium nitrate by evaporative dissociation.The presence of nitric acid as a result of the evaporative dissociationof ammonium nitrate was still identifiable due to the presence of theprotonated molecular ion peak occurring at 64 m/z. Thus, this testconfirms that heating of ammonium nitrate evolves nitric acid (NH₃)nitric oxide (NO) and nitrogen dioxide (NO₂).

EXAMPLE 4

The following example demonstrates that the fluorescent compounds do notrespond to nitric oxide (NO). On a 1200 L triple quadrupole massspectrometer, the system was setup with a 50/50 split configuration todeliver the effluent to both a sensor and the mass spectrometerconcurrently. One side of the split configuration was directed to asensor equipped with a preferred pH sensitive molecule coated sensingelement. In order to produce NO, a small amount of 2,4,6-trinitrotoluene(TNT) was placed into the injector and pyrolyzed at 425° C., whichimmediately evolves NO gas (30 m/z).

The mass spectrometer detected the NO; however, the fluorescent sensordid not produce a detectible change in response intensity. Therefore,the pH sensitive molecule compound did not respond to the presence ofNO.

Thus, the present invention is well adapted for the detection ofoxidizing salts. While preferred embodiments of the invention have beendescribed for the purpose of this disclosure, changes can be made bythose skilled in the art without departing from the spirit and scope ofthe present invention. Thus, the true nature of the current invention isdefined by the appended claims.

We claim:
 1. A detector assembly configured to detect trace amounts ofevaporative dissociation compounds derived from an oxidizing salt, thedetector assembly comprising: a sensor assembly including a solidsubstrate carrying a pH sensitive molecule, an excitation sourcepositioned to provide stimulating radiation to the pH sensitivemolecule, a light sensor to monitor a response of the pH sensitivemolecule to stimulation, and a heater suitable for adjusting thetemperature of said sensor assembly; a sampling tip assembly in fluidcommunication with said sensor assembly; a heater associated with saidsampling tip assembly, said heater suitable for maintaining thetemperature of the sampling tip assembly at a temperature between about90° and 350°; a gas movement pump in fluid communication with saidsampling tip and said sensor assembly, said gas movement pump configuredto move vapors from said sampling tip assembly to and along said solidsubstrate of said sensor assembly.
 2. The detector assembly of claim 1,wherein the pH sensitive molecule is selected from the group consistingof: SNARF®-5F, 5-(and-6)-carboxylic acid as represented by the followingstructure where the carboxylic acid group may be positioned at eitherthe indicated 5 or 6 position,

SNARF®-4F, 5-(and-6)-carboxylic acid as represented by the followingstructure where the carboxylic acid group may be positioned at eitherthe indicated 5 or 6 position,

5-(and-6)-carboxy SNARE®-1, as represented by the following structurewhere the carboxylic acid group may be positioned at either theindicated 5 or 6 position,

LysoSensor™ Green DND-153 as represented by the following structure,

2′,7′-difluorofluorescein as represented by the following structure,

2-[5-methoxy-2-(4-phenyl-quinoline-2yl)-phenyl]-ethanol as representedby the following structure

2-{2-[-(tert-butyl-dimethyl-silanyloxy)-ethyl]-4-methoxy-phenyl}-4-phenyl-quinolineas represented by the following structure


3. The detector assembly of claim 1, wherein said pH sensitive moleculeproduces a detectible response when stimulated by an excitation sourceemitting light radiation at wavelengths between about 325 nm and about700 nm.
 4. The detector assembly of claim 1, wherein said pH sensitivemolecule produces a detectible response when reacted with an acidcomponent of an oxidizing salt while undergoing excitation by anexcitation source emitting light radiation at wavelengths between about325 nm and about 700 nm.
 5. The excitation source in any of claims 3,wherein said excitation source emitting light radiation at wavelengthsbetween about 365 nm and about 410 nm.
 6. The excitation source in anyof claims 4, wherein said excitation source emitting light radiation atwavelengths between about 365 nm and about 410 nm.